1. Field of the Invention
The invention relates to a method and an apparatus for receiving a spread spectrum signal.
2. Description of the Related Art
Formation of a channel estimate is one of the most central operations in user signal detection in a receiver of a radio system, for example in a WCDMA (Wideband Code Division Multiple Access) receiver. The advantage obtained from antenna diversity in reception via several receiving antennas may be lost because of errors made in channel estimation.
The channel estimation error is minimized when adaptive channel estimation is used in a receiver. Adaptiviness means that the channel estimator adapts to the power density spectrum of the radio channel, i.e. the Doppler distribution. Since the Doppler distribution may in practice be different for each multi-path propagated component, adaptation has to be performed in a component-specific manner.
A disadvantage associated with the prior art solution is that in a receiver which implements antenna diversity, a single multi-path propagated component contains a small amount of energy, which makes estimation of the Doppler distribution width difficult.